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2. The gas pressure must be 4.0-10.5 inches w.c.
3. Table 10 offers some gas pipe sizing information. Refer
to the applicable gas code for more detailed sizing
information.
4. Run gas supply line in accordance with all applicable
codes.
5. Locate and install manual shutoff valves in accordance
with state and local requirements.
6. A sediment trap must be provided upstream of the gas
controls.
7. The unit and its individual shutoff valve must be
disconnected from the gas supply piping during any
pressure testing of that system at test pressures in
excess of 1/2 PSIG (3.45kpa).
8. The unit must be isolated from the gas supply system
by closing its individual manual shutoff valve during any
pressure testing of the gas supply piping system at test
pressures equal to or less than 1/2 PSIG (3.45kpa).
9. The unit and its gas connection must be leak tested
before placing it in operation.
10. Purge all air from gas lines.
SCH 40 METAL PIPE CAPACITY FOR 0.60 SPECIFIC GRAVITY
NATURAL GAS
NOMINAL PIPE SIZE @ 0.30” W.C. PRESSURE DROP
Nominal:
2
2½
3
4
5
Nominal:
1½
2
2½
3
4
Actual ID:
2.067
2.469
3.068
4.026
5.047
Actual ID:
1.61
2.067
2.469
3.068
4.026
Length (ft)
Length (ft)
10
4,020
6,400
11,300
23,100
41,800
10
3,520
6,790
10,800
19,100
39,000
20
2,760
4,400
7,780
15,900
28,700
20
2,420
4,660
7,430
13,100
26,800
30
2,220
3,530
6,250
12,700
23,000
30
1,940
3,750
5,970
10,600
21,500
40
1,900
3,020
5,350
10,900
19,700
40
1,660
3,210
5,110
9,030
18,400
50
1,680
2,680
4,740
9,660
17,500
50
1,480
2,840
4,530
8,000
16,300
60
1,520
2,430
4,290
8,760
15,800
60
1,340
2,570
4,100
7,250
14,800
70
1,400
2,230
3,950
8,050
14,600
80
1,230
2,370
3,770
6,670
13,600
80
1,300
2,080
3,670
7,490
13,600
100
1,140
2,200
3,510
6,210
124,700
90
1,220
1,950
3,450
7,030
12,700
125
1,070
2,070
3,290
5,820
11,900
100
1,160
1,840
3,260
6,640
12,000
150
1,010
1,950
3,110
5,500
11,200
125
1,020
1,630
2,890
5,890
10,600
175
899
1,730
2,760
4,880
9,950
150
928
1,480
2,610
5,330
9,650
200
814
1,570
2,500
4,420
9,010
175
854
1,360
2,410
4,910
8,880
250
749
1,440
2,300
4,060
8,290
200
794
1,270
2,240
4,560
8,260
300
697
1,340
2,140
3,780
7,710
150
704
1,120
1,980
4,050
7,320
350
618
1,190
1,900
3,350
6,840
300
638
1,020
1,800
3,670
6,630
400
560
1,080
1,720
3,040
6,190
350
587
935
1,650
3,370
6,100
Notes:
400
546
870
1,540
3,140
5,680
1. Inlet pressure - 11.0 in w.c.
Notes:
2. Pressure drop - 0.5 in w.c.
1. Inlet pressure - Less than 2 psi
3. Specific gravity - 1.50
2. Pressure drop - 0.5 in w.c.
4. Schedule 40 metallic pipe
3. Specific gravity - 0.60
5. Intended use - Pipe sizing between single
4. Schedule 40 metallic pipe
or second-stage (low pressure)
regulator and appliance.
Capacity in Cubic Feet of Gas per Hour
Pipe Size (in.)
Natural Gas
Undiluted Propane
Pipe Size (in.)
Capacity in Cubic Feet of Gas per Hour
Nominal:
2
2½
3
4
5
Nominal:
1½
2
2½
3
4
Actual ID:
2.067
2.469
3.068
4.026
5.047
Actual ID:
1.61
2.067
2.469
3.068
4.026
Length (ft)
Length (ft)
10
4,020
6,400
11,300
23,100
41,800
10
3,520
6,790
10,800
19,100
39,000
20
2,760
4,400
7,780
15,900
28,700
20
2,420
4,660
7,430
13,100
26,800
30
2,220
3,530
6,250
12,700
23,000
30
1,940
3,750
5,970
10,600
21,500
40
1,900
3,020
5,350
10,900
19,700
40
1,660
3,210
5,110
9,030
18,400
50
1,680
2,680
4,740
9,660
17,500
50
1,480
2,840
4,530
8,000
16,300
60
1,520
2,430
4,290
8,760
15,800
60
1,340
2,570
4,100
7,250
14,800
70
1,400
2,230
3,950
8,050
14,600
80
1,230
2,370
3,770
6,670
13,600
80
1,300
2,080
3,670
7,490
13,600
100
1,140
2,200
3,510
6,210
124,700
90
1,220
1,950
3,450
7,030
12,700
125
1,070
2,070
3,290
5,820
11,900
100
1,160
1,840
3,260
6,640
12,000
150
1,010
1,950
3,110
5,500
11,200
125
1,020
1,630
2,890
5,890
10,600
175
899
1,730
2,760
4,880
9,950
150
928
1,480
2,610
5,330
9,650
200
814
1,570
2,500
4,420
9,010
175
854
1,360
2,410
4,910
8,880
250
749
1,440
2,300
4,060
8,290
200
794
1,270
2,240
4,560
8,260
300
697
1,340
2,140
3,780
7,710
150
704
1,120
1,980
4,050
7,320
350
618
1,190
1,900
3,350
6,840
300
638
1,020
1,800
3,670
6,630
400
560
1,080
1,720
3,040
6,190
350
587
935
1,650
3,370
6,100
Notes:
400
546
870
1,540
3,140
5,680
1. Inlet pressure - 11.0 in w.c.
Notes:
2. Pressure drop - 0.5 in w.c.
1. Inlet pressure - Less than 2 psi
3. Specific gravity - 1.50
2. Pressure drop - 0.5 in w.c.
4. Schedule 40 metallic pipe
3. Specific gravity - 0.60
5. Intended use - Pipe sizing between single
4. Schedule 40 metallic pipe
or second-stage (low pressure)
regulator and appliance.
Capacity in Cubic Feet of Gas per Hour
Pipe Size (in.)
Natural Gas
Undiluted Propane
Pipe Size (in.)
Capacity in Cubic Feet of Gas per Hour
Table 10. Pipe Capacity for Natural Gas
The following are gas line sizing examples from the
National Fuel Gas Code. Size your gas lines properly,
based on your installation and all applicable codes.
3.B Gas Pipe Sizing
SECTION 4 Water Flow and
Headloss Data
4.A
General Water Flow Information
This appliance is a water-tube design that requires
water flow for operation. Boilers are generally used
in closed systems, so the manufacturer bases the
water flow data on temperature rise (difference
between boiler inlet and outlet temperature.) Water
heaters are used in open systems, with new water
constantly being introduced to the system. This brings
a constant supply of new minerals into the system, as
well. Minerals can cause scale to form on the inside
surfaces of water heater systems (heaters, tanks,
pipes, valves, and other components). Manufacturer
uses the water-tube design to its advantage by basing
the water flow data on water hardness, to assist in
minimizing mineral buildup in the heater’s waterways.
NOTE:
LAARS Heating Systems
